One of the key components of any computer system is a place to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disk drive. The most basic parts of a disk drive are a disk that is rotated, an actuator that moves a transducer to various locations over the disk, and electrical circuitry that is used to write and read data to and from the disk. The disk drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disk surface. A microprocessor controls most of the operations of the disk drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disk.
The transducer is typically housed within a small ceramic block. The small ceramic block is passed over the disk in a transducing relationship with the disk. The transducer can be used to read information representing data from the disk or write information representing data to the disk. When the disk is operating, the disk is usually spinning at relatively high revolutions per minute ("RPM"). These days common rotational speeds are 7200 RPM. Rotational speeds in high performance disk drives are as high as 10,000 RPM. Higher rotational speeds are contemplated for the future. These high rotational speeds place the small ceramic block in high air speeds. The small ceramic block, also referred to as a slider, is usually aerodynamically designed so that it flies over the disk. The slider has an air bearing surface ("ABS") which includes rails and a cavity between the rails. The air bearing surface is that portion of the slider that is nearest the disk as the disk drive is operating. When the disk rotates, air is dragged between the rails and the disk surface causing pressure, which forces the head away from the disk. At the same time, the air rushing past the depression in the air bearing surface produces a negative pressure area at the depression. The negative pressure or suction counteracts the pressure produced at the rails. The different forces produced counteract and ultimately fly over the surface of the disk at a particular fly height. The fly height is the thickness of the air lubrication film or the distance between the disk surface and the head. This film eliminates the friction and resulting wear that would occur if the transducing head and disk were in mechanical contact during disk rotation.
The best performance of the disk drive results when the ceramic block is flown as closely to the surface of the disk as possible. Today's small ceramic block or slider is designed to fly on a very thin layer of gas or air. In operation, the distance between the small ceramic block and the disk is very small. Currently "fly" heights are about 1-2 microinches. In some disk drives, the ceramic block does not fly on a cushion of air but rather passes through a layer of lubricant on the disk. A flexure is attached to the load spring and to the slider. The flexure allows the slider to pitch and roll so that the slider can accommodate various differences in tolerance and remain in close proximity to the disk.
Information representative of data is stored on the surface of the memory disk. Disk drive systems read and write information stored on tracks on memory disks. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the memory disk, read and write information on the memory disks when the transducers are accurately positioned over one of the designated tracks on the surface of the memory disk. The transducer is also said to be moved to a target track. As the memory disk spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the memory disk. Similarly, reading data on a memory disk is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disk. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disk drives, the tracks are a multiplicity of concentric circular tracks. In other disk drives, a continuous spiral is one track on one side of a disk drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held very accurately during a read or write operation using the servo information.
One of the most critical times during the operation of a disk drive occurs just before the disk drive shuts down or during the initial moment when the disk drive starts. When shutdown occurs, the small ceramic block or slider is typically flying over the disk at a very low height. In the past, the small block or slider was moved to a non-data area of the disk where it literally landed and skidded to a stop. Problems arise in such a system. Such a system is adequate for disk drives that had textured disk surfaces and which rotated at less than 7200 Revolutions Per Minute ("RPM"). To improve magnetic performance, disks now are formed with a smooth surface. To improve access times, disk stacks are now rotated at speeds of 10,000 RPM in a high performance disk drive. Stiction, which is static friction, occurs between the air bearing surface of the slider and the smooth disk surface. Forces from stiction, in some instances, can be high enough to separate the slider from the suspension. When the disk is rotated at 10,000 RPM, the velocity between the slider and disk is high. At high velocity, the kinetic energy that must be disappated when a contact between the disk and slider occurs is so high that particle generation is a distinct possibility. Still another problem is that landing a slider on the disk may limit the life of the disk drive. Each time the drive is turned off another contact start stop cycle occurs subjecting the slider to another high impact force which may cause the slider to chip or generate particles. The generated particles could eventually cause a head crash in the disk drive.
To overcome the stiction problem and to provide for a much more rugged design for disk drives used in mobile computers, such as portable computers and notebook computers, disk drive designers began unloading the sliders onto a ramp positioned on the edge of the disk. Disk drives with ramps are well known in the art. U.S. Pat. No. 4,933,785 issued to Morehouse et al. is one such design. Other disk drive designs having ramps therein are shown in U.S. Pat. Nos. 5,455,723, 5,235,482 and 5,034,837. A portion of the ramp is positioned over the disk. Before power is actually shut off, the actuator assembly moves the suspension, slider and transducer to a park position on the ramp. Commonly, this procedure is referred to as unloading the heads. Unloading the heads helps to insure that data on the disk is preserved since, at times, unwanted contact between the slider and the disk results in data loss on the disk. When starting up the disk drive, the process is reversed. In other words, the suspension and slider are moved from the ramp onto the surface of the disk and into a transducing position. This is referred to as loading the heads or sliders onto the disk.
Use of a ramp to load and unload the disk overcomes many aspects of the stiction problem. However, during the loading process and the unloading process, it seems that it is fairly common for the slider to contact the disk. In such situations, high friction forces can develop between the head and the disk. The high friction forces can cause slider and media damage. The contact with the disk in the disk stack rotated at 10,000 RPM or higher still has the potential to cause damage. Some manufacturer's simply sacrifice the portion of the disk at the outer diameter and devoted that space for loading and unloading to and from the disk. In other words, data is not kept at the outer diameter of the disk so that if disk contact occurs there is no possibility of losing data from damage to the disk. This design strategy is suboptimal. First of all, the area of the disk where the most information representative of data can be stored is the outer diameter of the disk. Giving up the outer diameter is like giving up the best located and most valuable real estate when developing a parcel of land. In addition, slider and disk contact will still occur and this could eventually generate particles and cause a disk crash. The damage is greater at higher rotational speeds of the disks in the disk drives. Thus, this problem will only get worse as higher RPM design points are set.
What is needed is a method for loading the sliders onto the disk without causing damage to the disk. What is further needed is a method for loading the sliders onto the disk without causing damage to the heads. Also needed is a method for avoiding contact or for controlling the parameters which determine the severity of the contact between the disk and the slider so that the amount of damage resulting from a contact will be minimal. Also needed is a system which is easy to manufacture and a system that also does not require adjustment. The system must also be rugged and stable over time. In other words, the system must be able to last for the life of the drive. The system must also be made of materials with minimal outgassing properties so that contaminants will not be added to the disk drive enclosure or contaminant the lubricant on the disk. The system must also provide gimballing of the slider with respect to the suspension.